The present disclosure relates to a dry etching method, and pertains to a field of semiconductor technologies.
Dry etching (or dry etching technique) is a technique for thin film etching using plasma. Gases have the following two characteristics when existing in the form of plasma: on one hand, chemical activity of the gases in plasma is much higher than that in a normal state, the appropriate gas is selected according to different etched materials, quicker reaction with the materials can be realized to achieve the objective of etching and removal; and on the other hand, the plasma can also be guided and accelerated by an electric field so that the plasma has certain energy, and thus when the plasma bombards the surface of an object being etched, the plasma can hit out atoms of the materials of the etched object. In this way, the objective of etching can be achieved by physical energy transfer. Therefore, dry etching is a result of balance of a physical process and a chemical process on a wafer surface. The general dry etching method is as below: molecules or molecular groups capable of producing ion chemical reaction with a thin film are generated using glow discharge of a particular gas (or a mixed gas) under a pressure of 10˜1,000 Pa, and the generated reaction product is volatile. Next, the generated reaction product is pumped away in a low-pressure vacuum chamber. In this way, etching can be achieved.
At present, in a deep via-hole plasma etching process of preparation for a low-temperature polysilicon thin-film transistor array substrate, positive/negative charges may be accumulated in a local area of the substrate due to nonuniformity of distribution of the plasma in an etch chamber. Moreover, the presence of a plasma sheath makes ions and electrons distribute in different locations: the electrons are accumulated on a side wall of an etching trench, whereas the ions are accumulated at the bottom of the trench. As shown in FIG. 1, to etch a via hole reaching a metal layer 4 on an insulating layer 3, in the process of etching, some microetching 2 may occur because a direction of physical etching is changed due to an effect of the electrons accumulated on the side wall of the etching trench on positive ions in etching gas, wherein 1 represents a photoresist layer, 5 represents a buffer layer, and 6 represents the substrate. The microetching may cause a decrease of stability and reliability of a liquid crystal display panel.